Reconfigurability of an electro-magnetic (EM) surface is often desired when a variety of RF functions are needed and there is a space or weight limitation at the location on which the electromagnetic structure is to be mounted. Reconfigurability of an EM surface can also save assembly time and material costs of having to swap out RF apertures when a new RF application is needed.
J. D. Wolfm N. P. Lower, L. M Paulsen, J. P. Doene, and J. B. West describe, in “Reconfigurable radio frequency (RF) surface with optical bias for RF antenna and RF circuit applications”, U.S. Pat. No. 7,965,249, issued Jun. 21, 2011, a reconfigurable antenna with optical actuation of photoconductive switches between small metallic patches forming a pixelated surface. Light emitting diodes (LEDs) are used to actuate the photoconductive switches, which has the disadvantage of requiring constant power input to drive the LED's to keep the switches closed. In a large EM structure very high power would be required. Lacking in the description is any teaching on what happens to an RF feed when the antenna is reconfigured
L. Zhouyuan, D. Rodrigo, L. Jofre, and B. A. Cetiner, in “A new class of antenna array with a reconfigurable element factor,” IEEE Trans. Antenna Propagation., Vol. 61, No. 4, April 2103, pp. 1947-1955 describe a reconfigurable element that uses a parasitic pixel array of small metallic patches which are reconfigured using switches to provide beam steering or polarization switching. A non-reconfigurable patch antenna is used as the driver for the parasitic pixels, which limits the bandwidth to the patch size.
Other examples of pixelated structures for reconfigurable antennas are described by E. K. Walton, and B. G. Montgomery, in “Reconfigurable antenna using addressable pixel pistons,” U.S. Pat. No. 7,561,109, issued Jul. 14, 2009; E. Rodrigo and L. Jofre, in “Frequency and radiation pattern reconfigurability of a multi-size pixel antenna,” IEEE Trans. Antenna Propagation., Vol. 60, No. 5, May 2012, pp. 2219-2225; and A. G. Besoli and F. De Flaviis, in “A multifunction reconfigurable pixeled antenna using MEMS Technology on printed circuit board,” IEEE Trans. Antennas and Propagation, Vol. 59, No. 12, December 2011. However, all of these use mechanical or electronic switches which require a complicated and RF degrading direct current (DC) bias network.
What is needed is an improved reconfigurable electromagnetic surface. The embodiments of the present disclosure answer these and other needs.